1. Dipartimento di Fisica, Università degli Studi di Torino, via Giuria 1, Torino 10125, Italy
2. ISI Foundation, via Alassio 11/C, Torino 10126, Italy
3. Aizoon Technology Consulting, Str. del Lionetto 6, Torino, Italy
4. Sociology and Economics of Networks and Services Department, Orange Laboratories, Issy-les-Moulineaux, France
5. Sorbonne Universités, UPMC Univ Paris 06, INSERM, Institut Pierre Louis d’Epidémiologie et de Santé Publique (IPLESP, UMR–S 1136), Paris, France